This invention provides an improved process for preparing polymer bound hindered amine light stabilizers by reacting 4-amino-substituted polyalkylpiperidines with anhydride containing polymers or copolymers in a melt blending step to form imidized copolymers containing pendant hindered amine light stabilizing groups.
It is known in the prior art to attach 4-amino-2,2,6,6-tetramethylpiperidine and 4-amino-1,2,2,6,6-pentamethylpiperidine to maleic anhydride copolymers in solution. Ger Offen 3,024,525 describes the reaction of cationic maleic anhydride homo- and copolymers with 4-amino-2,2,6,6-tetramethylpiperidine in solution to form the corresponding imide containing polymers.
Maleic anhydride modified polyolefins have been reacted with 4-amino-2,2,6,6-tetramethylpiperidine to form the corresponding N-substituted maleimide modified polyolefins (U.S. Pat. No. 4,520,171). The reactions were all run by refluxing the amine and maleic anhydride copolymer in an aromatic solvent and removing water as it formed.
GB 2,145,100A discloses the reaction of maleic anhydride copolymers with polalkylpiperidine derivatives. It is stated that reactions of copolymers of maleic anhydride with R.sup.15 -NH.sub.2 (where R.sup.15 is a polyalkylpiperidyl group) are preferably carried out in a solvent.
The imidization of maleic anhydride copolymers with ammonia or primary amines is normally carried out in a solvent or in a suspension. Various solvents that have been used for the imidization step include toluene, xylene, chlorobenzene, tetrahydrofuran, dimethylformamide, dimethylsulfoxide, methyl ethyl ketone and acetone. Imidizations have also been run by suspending the maleic anhydride copolymers in aqueous solutions. Imidizations have also been run by including anilines such as aniline in the polymerization system. One of the problems that occurs when the imidization is run in a solvent is the long reaction time required to complete the imidization step (generally about 5-12 hours at the reflux temperature of the solvent). (Jpn Kokai Tokyo Koho JP 57,125,242 and JP 57,125,141; CA 98 35543e and 35544f; JP 82,55,901; CA 97 93354j; U.S. Pat. No. 3,998,907). Usually the imidized polymer is isolated by precipitating it into a non-solvent and filtering off the polymer. This requires the recovery and purification of a large amount of solvent.
There are isolated cases known where the imidization step is carried out in a melt blending step. JP 82,100,104 (CA 97 199015g) states that rubber modified styrene-maleic anhydride copolymers can be imidized with NH.sub.3 or primary amines at 80-350.degree. C. in solution, dispersion in hydrocarbon solvents or in the molten state.
U.S. Pat. No. 4,544,682 describes the reaction of a brominated primary aliphatic amine with a copolymer of a monoalkenyl aromatic monomer and an ethylenically unsaturated anhydride in a melt blending step such as in an extruder at a temperature at or above the melting point of the copolymer.
Ger. Offen De 3,430,802 (3/6/86) (CA 104 207938y) discloses the attachment of primary amines to maleic anhydride copolymers in an extruder at temperatures of 150-300.degree. C. with an average residence time of 0.5-30 minutes. Japanese Pat. No. 83 180,506 discloses the attachment of primary amines (toluidine) to SMA in a first extruder and then feeding the extrudate to a second vented extruder.
U.S. Pat. No. 4,591,619 discloses a process for producing an imidized copolymer by reacting a rubber modified styrene-maleic anhydride copolymer with ammonia or a primary amine in the presence of a tertiary amine at a temperature of 80 to 350.degree. C.